David Koch at the unveiling of of the Metropolitan Museum of Art's new David H. Koch Plaza.Invision for David H. Koch Foundation

Nothing infuriates the left more than the generosity of David Koch, he of the notorious Koch Brothers, who keep on pursuing both activist conservative politics and pure philanthropy.

Three dozen scientists, joined by groups like the Sierra Club and Greenpeace, are demanding that all science museums cut ties with any people or firms that, like the Kochs, “profit from fossil fuels.”

More: They want David Koch kicked off the boards of the Museum of Natural History in New York and of the Smithsonian — to which he’s given $70-plus million.

Why? The Koch brothers also fund groups that question the political consensus on climate change — so their money is “tainted.”

Now, both museums say they have no intention of booting Koch or anyone else. They also note that permanent exhibits he’s endowed at the Smithsonian specifically address the impact of climate change.

In other words, it’s an utterly phony issue.

As with the bid to block Koch’s $100 million gift to New York-Presbyterian Hospital, it’s all about the left’s crazed obsession with its favorite political whipping boys.

David Koch has given $1.3 billion to civic improvement, much of it in New York. When Bill Gates does that, he’s justifiably hailed; the Koch brothers get demonized as “un-Americans” trying to “launder their image.”

But don’t expect Greenpeace to ante up next time a museum needs a new wing funded.